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56 Cards in this Set
- Front
- Back
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Structure of the Earth |
Iron & nickel core, mantle, crust |
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Tectonic plates |
Crust and upper mantle are cracked into large pieces called tectonic plates. They move around- few cm per year |
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What shows the movement of tectonic plates? |
Magnetic clues in rocks. When tectonic plates move apart under the sea, exposed mantle rises up and a new crust solidifies. New crust is magnetised by Earth's magnetic field. Normal or reverse polarity. pattern of normal/reversed polarised rocks used to estimate age of parts of crust Track slow movement of plates |
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Sedimentary rocks contain clues |
Look at features of rocks. Fossils- remains/imprints of dead organisms tells age of rock. Conditions it was formed in. Shells, ripples,shapes of grains (water-borne or air-blown) |
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Minerals in the crust- formed by different processes |
Sedimentation, Evaporation, Dissolving, Erosion, Mountain building. Chemical industries grow. |
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Describe Limestone |
-Sedimentary rock from seashells -over millions of years layers of sediment get buried. Weight pressing down squeezes out water -natural mineral cement |
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Describe coal |
-Black in colour -Sedimentary -Mainly carbon -lots of impurities |
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Where is salt found? |
Rock salt- salt and impurities, found in underground deposits. Massive deposits in Cheshire & Teeside, UK |
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What is normal salt mining? |
Physical extraction of salt Rock salt is drilled, blasted, dug out, brought to surface. Mostly used on roads to stop ice forming. - salt can be seperated- flavour food, making chemicals |
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What is solution mining? |
Water is injected into salt deposit. Dissolves to make brine. Pressure forces brine to surface. Brine stored in wells and pumped to refining plant. Impurities removed. Brine boiled, water evaporates, salt left. Most table salt, chemical production. |
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How do these methods of mining salt impact the environment? |
Pollution- mining requires a lot of energy. Subsidence- land above collapse into holes Risk reduced by filled in caverns. |
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Another method of obtaining salt |
in hot countries, evaporating seawater. Shallow pools, left in sun, salt is collected. Purest salt- almost 100% NaCl |
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How is salt used in food production? |
To enhance flavour. Mostly in processed foods. As a preservative- when added to meat, kills bacteria |
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What are health issues with the use of salt? |
High intake= High blood pressure, stroke, heart attacks Increases risks of stomach cancer, osteoporosis, renal failure. |
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Government issues guidelines for salt intake |
Watchdogs, Food Standards agency. GDA risk assessments, advise the public. Food manufactures still include salt to support sales. Cost of reformulating recipes is great. |
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How is salt important for the chemical industry? |
They electrolyse brine- they pass an electric current through it. Causes chemical change- splits solution into Hydrogen, Chlorine and Sodium Hydroxide. |
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Electrolysis of Brine- 1) Chlorine What are the uses? |
Disinfectants Killing bacteria Household bleach Plastics HCL Insecticides |
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Uses of hydrogen |
ammonia turning oils into fats- margarine fuels welding and metal cutting |
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Uses of Sodium Hydroxide |
Very strong alkali Soap Ceramics Organic chemicals Paper pulp Oven cleaner Household bleach- when it reacts with Chlorine. |
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Environmental impact of large scale electrolysis |
Pollution Uses finite resources Mercury and asbestos are used- they are toxic, can cause cancer, contaminate rivers |
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Chlorine used for water treatment |
small amounts added to water to kill bacteria Prevents algae growth kills disease causing microorganisms |
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Why is chlorine important for water treatment? |
it lowers death rates- less people die from water-bourne diseases. Over 1bn dont have access to clean water- very expensive. Chlorine increases life expectancy. V important. |
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What are the disadvantages of chlorinating water? Why do people object? |
Chlorine reacts with compounds to form chlorinated hydrocarbons- carcinogenic. Chlorine gas irritates respiratory system. Liquid chlorine causes severe chemical burns. Some say we dont get a choice- forced 'mass medication' |
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What are Alkalis? |
Type of chemical. A compound that forms hydroxide ions when dissolved in water. |
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What is a neutralisation reaction? |
Acid and an alkali react to form a salt and water. The products are neutral. |
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What are 2 types of neutralisation reactions? |
Acid+ Hydroxide= Salt + water Acid + Carbonate= Salt + water + carbon dioxide |
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What are the uses of alkalis? |
Farmers use alkalis to neutralise acidic soils. Make chemicals for natural dyes. Convert fats and oils into soap. Manufacture glass. |
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'History' of alkalis |
Used for hundreds of years. People relied on traditional sources- burnt wood & stale urine. 19th Century- Shortage |
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The LeBlanc Process |
Alkalis had to be manufactured on a large scale. Process invented to make sodium carbonate. Sodium chloride mixed with sulfuric acid then heated with charcoal and limestone. |
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Problems of the LeBlanc Process |
Very Polluting. Large volumes of acidic hydrogen chloride- damaged environment. A lot of solid waste. Released toxic Hydrogen Sulfide. Foul smell of rotten eggs. |
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Products made using Chemistry |
Drugs, paints, dyes, used in industry, used in the home. agricultural chemicals, plastics, metals, fuels. So many chemicals- Cannot be tested thoroughly. Not enough data about risks. |
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Problems with toxic chemicals |
Stay in environment if not broken down. End up in water ways/ eaten by animals. Spread over large area. Passed along food chains. Harm to animals, even humans |
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How can pesticides be harmful? |
1) Insecticide seeps into river 2) small plants take it in 3)Tiny animals eat the plants 4) Small fish eats tiny animals 5) Eel eats small fish 6) Otter eats eels Toxic to creatures. |
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How are plasticisers harmful? |
Leach out into water sources. Also toxic. |
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Life Cycle Assessments- Stage 1 |
Choice of material: Water mostly needed. Metals mined and extracted. Lots of energy= pollution. Raw materials- No- renewable and finite. E.g: Crude oil: finite and causes lots of pollution. |
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LCA- Stage 2 |
Manufacture: Lots of energy. Pollution: CO, HCl. How to dispose/ recycle. |
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LCA - Stage 3 |
Using the product- can also damage environment. Paint; toxic fumes Burning; greenhouse gases Fertilisers; can leech out, damage ecosystem |
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LCA- Stage 4 |
Product Disposal: Landfill site. Takes up space, pollutes. Might be incinerated(burnt); air pollution Some can be recycled- processed & re- used |
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as volcanic lava solidifies, igneous rocks are formed . magnetic materials in the lava line up along the Earths magnetic field |
the earths magnetic field changes over time. geologists can date rocks and track the slow movement of continents using changes in magnetic patterns, linked to radioactivity. this evidence supports plate tectonic theory |
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there was limestone in the peak district. limestone formed while Britain was covered by sea: |
- shellfish died forming sediments on the sea bed - sediments compacted and hardened to form limestone, a sedimentary rock - tectonic plate movements pushed the rock to the surface - gradually the rocks above were eroded away until the limestone was exposed |
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coal was found in south Lancashire. coal contains fossils of the plants that formed it |
coal formed in wet swampy conditions when plants like trees and ferns died and became buried. this excluded oxygen, slowing down the decay
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salt formed while Cheshire was covered by a shallow sea: |
- rivers brought dissolved salts into the sea - climate warming evaporated the water, leaving salt that mixed with sand blown in by the wind - rock salt formed and was buried by other sediments |
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limestone contains bits of shell-fragments from sea creatures |
rock salt contains different-shaped water-eroded grains and wind-eroded grains |
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salt is used in: - the food industry - as a source of chemicals - to treat icy roads in winter |
salt can be obtained from: - collecting and evaporating sea water - mining underground deposits of rock salt |
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rock salt is spread on icy roads because: - the rock is insoluble but the sand in the rock salt gives grip - it shows up so people know when roads have been gritted - the salt in solution lowers the freezing point, preventing ice forming as easily |
solution mining- water is pumped at high pressure into the rock salt, he salt dissolves and the salt solution is pushed to the surface |
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salt is a valuable raw material, but its extraction can have an environmental impact |
- mining rock salt and solution mining can cause subsidence. about half the rock salt cannot be mined, as it is left in for support - mining can allow water in mines, which may let salt leach out into water supplied, contaminating them - evaporating salt from sea water takes up large areas and spreads salt into the local environment, damaging habitats |
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salt is used in food as: - flavouring - preservative |
a higher salt level prevents bacteria growth - many people are worried about salt intake which can cause high blood pressure, heart failure and srokes |
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alkalis neutralise acids to make salts, called neutralisation |
acid+ alkali--> salt + water |
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alkalis are used for: - dying cloth -neutralising acid sol - making soap - making glass |
stale urine and ash from burnt wood were used in the past as a source of alkalis |
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the first alkali to be manufactured was lime(calcium oxide). this was done by heating limestone (calcium carbonate) in a lime kiln, using coal as fuel |
lime us used for: - neutralising acidic soils - making glass when heated with sand - removing impurities when iron is made |
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the leblanc process made sodium carbonate by reacting salt and limestone, heated with coal. but it gave off large amounts of hydrogen chloride. and produced heaps of solid waste, called galligu, that slowly released hydrogen sulfide |
later, a process was invented to change the harmful hydrogen chloride into useful substances: - chlorine used to bleach textiles prior to dying - hydrochloric acid, which is a starting material for making other chemicals |
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chlorine can be made by reacting hydrochloric acid and manganese dioxide |
- oxidation converts hydrogen chloride into chlorine - compounds have different properties from those of the elements they contain |
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chlorine is added to water supplies to kill microorganism. chlorination killed water-borne microorganisms that cause diseases like cholera and typhoid |
chlorine is a toxic gas and can affect human health if too much is present in water |
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electrolysis breaks up compounds using an electric current |
the electrolysis of brine(sodium chloride solution) makes: - chlorine gas - hydrogen gas - sodium hydroxide solution |
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industrial uses of these products are: - chlorine for making plastics like PVC, in medicines and crop protection - hydrogen for making margarine, as rocket fuel, in fuel cells in vehicles - sodium hydroxide for paper recycling, industrial cleaners and reining aluminium |
large amounts of electricity is needed for electrolysis, so its expensive |
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brine electrolysis is one of the many widely used industrial processes. while the products have many uses, they can have an environmental impact: |
- chlorine products, e.g. from fridges and aerosols, are linked to ozon depletion and have been banned - chlorine used in paper bleaching releases dangerous dioxins, increasing the risk of cancer - the mercury diaphragm method of electrolysis, which is still used, releases mercury waste. this can enter the food chain and is a cumulative poison - plastics made using chlorine are non-biodegradable |
